Gas springs of the generic type are known from U.S. Pat. No. 3,656,593. Elevating mechanisms for chairs, tables and the like assembled by using such longitudinally adjustable gas springs are for instance known from U.S. Pat. No. 3,711,054. U.S. Pat. No. 4,979,718 discloses to encase the housing of the gas spring itself in an additional suspension tube and to guide the latter for displacement in the guide tube of the elevating mechanism. In such gas springs the familiar problem occurs that the piston rods do not extend in absolute alignment with the axis of the housing or the additional suspension tube. The guide bushes usually arranged in the guide tubes can increase such misaligments so that the free end of the piston rod fixed in a bottom plate of the guide tube clearly deviates from the central axis of the guide tube, which should actually coincide with the central axis of the gas spring. As a result of these misalignments the free end of the piston rod held in the bottom plate of the guide tube moves at right angles to the bottom plate during entering or exiting movements of the gas spring. The disks of the axial rolling bearing make clicking noises when this rolling bearing is moved to and fro on the bottom plate of the guide tube.